Methods for in situ detecting proximity of two targets of interest featuring an antibody conjugated with a cleavable bridge component having a detectable moiety and an antibody conjugated with a non-cleavable bridge component. The bridge components each have a chemical ligation group adapted to form a covalent bond under particular conditions and when the targets are in close proximity. Following covalent bond formation, the cleavable bridge component can be cleaved from the antibody, effectively transferring the detectable moiety to the non-cleavable bridge component. Detection of the detectable moiety is indicative of the targets being in close proximity. The methods are compatible with both chromogenic and fluorogenic detection systems. The methods may be used to perform assays wherein one or more than one proximity event is detected on the same slide.

Described herein are biosensor microarrays comprising detector polypeptide monolayers substantially free of contaminants. Also provided are methods for generation of such biosensor microarrays by capture of polypeptides by arrays comprising capture moieties and associated sensors.

Compositions and methods for identifying glucuronylated protein drug products are provided.

Chemoproteomic methods for detecting and profiling electrophilic post-translational modifications (PTMs) and oxidative PTMs in proteins are described. The methods including contacting a proteomic mixture with a probe having hydrazine and an affinity handle to form a covalent linkage between the hydrazine moiety of the probe and the endogenous electrophilic PTM or the endogenous oxidative PTM. The resulting derivatized proteins are labelled with an tag via a click chemistry reaction. The labelled proteins can then be detected or profiled using techniques such as, for example, fluorescence imaging or mass spectrometry. Also described are protein conjugates having a covalent linkage formed by reaction of a hydrazine or oxyamine moiety of a probe with an electrophilic or oxidative PTM of a protein.

Methods for the large scale identification of post-translational modification states of proteins and enzyme activities for carrying out post-translational modification reactions involve the analysis of functional extracts from fresh and frozen samples using protein arrays. The methods and kits of the present invention can be used to analyze and characterize compounds for their effects on post-translational modifications and their pathways. The methods and kits can also be used to diagnose and characterize a wide variety of diseases and medical conditions, including cancer, neurodegenerative diseases, immune diseases, infectious diseases, genetic diseases, metabolic conditions, and drug effects using cells or body fluids of a patient.

Bead arrays suitable for analysis by mass spectrometry are disclosed. In an embodiment, a bead array includes multiple reactive sites, each of the reactive sites being capable of binding multiple distinct target analytes.

Methods and system for identifying and/or quantifying a protein are provided herein.

Methods and system for identifying and/or quantifying a protein are provided herein.

Disclosed are compositions and methods for performing a proteomic analysis. Particularly disclosed are compositions and methods for preparing a sample for quantitative single-cell proteomics.

This disclosure provides methods, systems, and compositions of matter for studying solvent accessibility and three-dimensional structure of biological molecules. A plasma can be used to generate marker radicals, which can interact with a biological molecule and mark the solvent-accessible portions of the biological molecule.